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 A034887 Number of digits in 2^n. 20
 1, 1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 10, 10, 11, 11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 15, 15, 15, 16, 16, 16, 16, 17, 17, 17, 18, 18, 18, 19, 19, 19, 19, 20, 20, 20, 21, 21, 21, 22, 22, 22 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 COMMENTS The sequence consists of the positive integers, each appearing 3 or 4 times. - M. F. Hasler, Oct 08 2016 LINKS T. D. Noe, Table of n, a(n) for n = 0..10000 Eric Weisstein's World of Mathematics, Mersenne Number FORMULA a(n) = floor(n*log(2)/log(10)) + 1. E.g., a(10)=4 because 2^10 = 1024 and floor(10*log(2)/log(10) + 1 = 3 + 1 = 4. - Jaap Spies, Dec 11 2003 a(n) = A055642(2^n) = A055642(A000079(n)). MAPLE seq(floor(n*ln(2)/ln(10))+1, n=0..100); # Jaap Spies, Dec 11 2003 MATHEMATICA Table[Length[IntegerDigits[2^n]], {n, 0, 100}] (* T. D. Noe, Feb 11 2013 *) IntegerLength[2^Range[0, 80]] (* Harvey P. Dale, Jul 28 2017 *) PROG (Magma) [#Intseq(2^n): n in [0..100] ]; // Vincenzo Librandi, Jun 23 2015 (PARI) A034887(n)=n*log(2)\log(10)+1 \\ or: { a(n)=#digits(1<

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Last modified December 6 10:03 EST 2022. Contains 358630 sequences. (Running on oeis4.)